1. Field of the Invention
The present invention is directed to a color image reproducing system for predicting the appearance of a printed image prior to finally producing it with a simulated image reproduced on a monitor device whose appearance agrees highly accurately with the printed image by taking into account periodic and random noises introduced in the printed image due to characteristics of a printing device and an image to be printed.
2. Description of the Related Art
In recent years, there have widely been used printing systems for reading an image from an original document such as a photograph, a painting, or the like or processing image data supplied from an image input device and generating printed material using a film original plate or a press plate.
Such a printed material is produced through a number of processing steps. More specifically, color separation films of Y, M, C, K are generated on the basis of image data supplied from an image input device, and presensitized plates are exposed to color images through the color separation films. Then, the color images on the presensitized plates are developed, and the presensitized plates are set on a printing press to produce a printed material. The printed material which is finally produced depends on various printing conditions (output conditions) including the paper, inks, and water used, the type of the printing press, and the screen ruling and dot shape which are employed for the formation of dot-matrix images. In producing a printed image based on the above complex processing steps and conditions, it is important to generate a simulated image in advance by outputting processed image data on a CRT, a printer, or the like, to determine whether printing conditions to produce a printed image from the image data are appropriate or not based on the simulated image, and to adjust the conditions if necessary.
The simulated image is made equivalent to a printed image by colorimetrically equalizing the individual colors of the pixels of the simulated image to those of the printed image and equalizing optical characteristics depending upon the output method and resolution of output systems used, and the properties of a support layer for the printed image such as optical dispersion, surface reflections, etc.
The printed image generated by the printing press is represented as a continuous gradation image using halftone dots, and hence contains a rosette pattern or moire characteristic of images formed from halftone dots. Images generated by ordinary printers or CRTs, however, do not contain such a rosette pattern or moire as these images are continuous gradation images represented by density or luminance changes. Therefore, it is difficult to produce equal images with the printing press and the printer or CRT as generated images have different qualities because of different output methods used. Generally, the printing press which generates printed images and the printer or CRT which generates simulated images have different resolutions. Usually, the printer or CRT which generates simulated images have a resolution lower than the printing press which generates printed images. If the resolution and accuracy of the printer or CRT which generates simulated images are increased so as to be equivalent to those of the printing press, then the printer or CRT will be unduly expensive and specialized.